Impact of coronary calcium score as gatekeeper for coronary CT angiography

Purpose: The aim of this study is to determine the thresholds of coronary calcium score (CCS) above which coronary CT angiography (CCTA) should be aborted because of the limitation of diagnostic ability. Methods: Consecutive 500 symptomatic patients (64±12 years old) who were referred for diagnostic CCTA were investigated. Subjects underwent CCS measurements and CCTA using 64-slice high definition CT. Inconclusive CCTA was defined as the case with at least one non-evaluable segment in major coronary vessels due to heavy calcification. Results: Mean CCS of all 500 patients was 152±368 (0-2595). Of these, 17 (3%) resulted in inconclusive CCTA due to heavy calcification. The sensitivity and specificity curves identified 540 as optimal thresholds of CCS to predict inconclusive CCTA (sensitivity 0.94, specificity 0.94). Area under the curve of ROC analysis was 0.98. Among the 17 cases with inconclusive CCTA (CCS 1380±675), 14 (82%) underwent catheter coronary angiography (CAG), of these, 13 (93%) needed subsequent coronary revascularization (PCI 10, CABG 3). Conclusions: In cases with inconclusive CCTA due to heavy calcification, high prevalence of severe coronary artery disease was revealed with CAG. CCS>540 should alert us to potential diagnostic limitation with CCTA, thus further evaluation with CCTA is not warranted as those patients should be referred to CAG to avoid repeat radiation exposure.